Valvular heart diseases are among the most prominent causes of heart failure and premature cardiac death. Aortic valve stenosis is a very common valvular disease. This disease is often treated by implanting an artificial aortic valve via an open cardiac surgery. This is, however, a very invasive and expensive treatment. In addition, it is considered too high risks or contraindicated for many patients.
In the last decade, techniques for minimally invasive aortic valve implantation have been developed that offer a new treatment option. An alternative method for high-risk patients that cannot undergo an open-heart surgery for aortic valve replacement is a trans-catheter aortic valve implantation (TAVI). In this technique, an artificial valve is mounted on a stent which is delivered through a catheter, either transfemoral, transsubclavian, or trans-apical, under X-ray guidance, and then expanded in-place.
Although TAVI is less invasive, its long-term outcome is unclear. A current discussion is therefore, if TAVI is also beneficial for patients with only intermediate risk for valve replacement. Because their expected lifetime is much longer, the long-term benefit of the TAVI implant must be ensured.
If the TAVI implant is placed too low, i.e. reaching too far into the left ventricular outflow tract, it can impair movement of the anterior mitral leaflet. Case reports demonstrated that contact between the implant and the mitral valve leaflet led to mitral endocarditis and leaflet aneurysms, see e.g. Piazza, N. et al.: “Two cases of aneurysm of the anterior mitral valve leaflet associated with transcatheter aortic valve endocarditis: a mere coincidence?”, in Journal of Thoracic and Cardiovascular Surgery 140(3) (2010) e36-e38.
First, repetitive friction between the implant and the leaflet could damage the leaflet surface. Second, the implant could act as an endocarditis bridge that favors the spread of aortic valve endocarditis to the mitral valve. Especially, the slow tissue degeneration caused by repetitive friction might become more relevant the longer the implant is present.
Therefore, preparing and planning medical procedures like TAVI before beginning an actual operation is of utmost importance. The treatment planning should particularly make sure to avoid the above explained friction between the implant and any anatomical structure of the heart. Such medical imaging procedures are also important to guide the implantation during the surgery (in real-time), since the aortic valve anatomy is not clearly visible when using X-ray imaging.
Wächter et al.: “Patient specific models for planning and guidance of minimally invasive aortic valve implantation”, MICCAI 2010, part I, LNCS 6361, pp. 526-533, 2010, Springer-Verlag Berlin Heidelberg 2010, present a method to extract the aortic valve anatomy from CT images. The therein presented method allows for detection of anatomical landmarks by exploiting the model-based segmentation. This allows to receive a fairly accurate model, in particular of the aortic valve and the coronary ostia. The method is also described in WO 2011/132131 A1, a prior patent application filed by the applicant.
Capelli, C. et al.: “Finite Element Strategies to Satisfy Clinical and Engineering Requirements in the Field of Percutaneous Valves”, in Annals of Biomedical Engineering, vol. 40, No. 12, December 2012, pp. 2663-2673 discloses a study showing that beam elements are a convenient choice toward a practical and reliable clinical application of finite element modelling of percutaneous devices for valve implantation. Similar aspects are disclosed in Capelli, C. et al.: “Patient-specific simulations of transcatheter aortic valve stent implantation”, in Medical & Biological Engineering & Computing, Springer, Berlin, vol. 50, no. 2, pp. 183-192.
US 2011/153286 A1 discloses a method and system for virtual percutaneous valve implantation. A patient-specific anatomical model of a heart valve is estimated based on 3D cardiac medical image data and an implant model representing a valve implant is virtually deployed into the patient-specific anatomical model of the heart valve. A library of implant models, each modeling geometrical properties of a corresponding valve implant, is maintained. The implant models maintained in the library are virtually deployed into the patient specific anatomical model of the heart valve to select an implant type and size and deployment location and orientation for percutaneous valve implantation.
However, there is still need for further improvement of such medical planning systems.